The present invention relates to a cutting instrument having a variety of sensors integrated therein. More particularly, the invention relates to a blade having a sensor or sensors formed thereon, wherein the sensors are mounted adjacent the cutting surface to allow measurement of the physical characteristics of the blade and a workpiece or tissue.
Cutting instruments exist for a myriad of applications, ranging from very specialized applications such as surgical scalpels, to industrial applications and common consumer applications.
Surgery continues to be one of the most delicate and risky medical procedures. Before making an incision into tissue, surgeons are required to identify what type of tissue is being incised, such as fatty, muscular, vascular or nerve. This task is greatly complicated by the fact that human anatomy differs slightly from person to person. The failure to properly classify tissue before making an incision can have severe adverse consequences. For example, if a surgeon fails to properly classify a nerve and cuts it, then the patient can suffer effects ranging from a loss of feeling to loss of motor control.
Thus, it would be useful to surgeons to be able to sense during surgery, and more particularly during the actual cutting operation, certain characteristics that would help to identify and classify the substrate tissue. For example, by sensing the amount of force being applied with a blade, the resistance of the tissue can be measured and can be used to assist in the classification of the tissue. Sensing the different pressure characteristics of material surrounding a blade, for example in the surrounding fluid, can help to classify the type or types of tissue surrounding the blade or the regions of the body being cut by the blade. Sensing the density of the tissue in proximity with the blade can also be used to assist in the identification of that tissue. Finally, as noted above, sensing the presence of nerve tissue can prevent the inadvertent cutting thereof. Moreover, the ability to sense the type of tissue in proximity with or cut by a blade would not only be useful to provide real time feedback for surgeons during surgery, but would also be useful if recorded for later use for tracking purposes.
Temperature can also be used to monitor the usage of a blade. For example, by monitoring the time for which a blade is at approximately 98.6 degrees Fahrenheit, the length of time that the blade has been in use can be determined. Also, information relating to the extent and direction of movement of a blade can useful both while the blade is being used and afterward for monitoring purposes, such as to measure the amount of cutting done in a procedure.
The ability to sense one or more of the parameters just described would also be useful in non-medical/surgical applications. For example, in connection with a consumer blade such as a razor blade, measurement of one or more of these parameters may be used to give consumers information regarding the cutting force applied to the blade, the materials being cut, and to estimate the sharpness of the blade. Furthermore, the manufacturers that design consumer blades may use the measured parameters to assess the impact of cutting tool design changes. For example, a razor blade manufacturer could quantify the changes in applied force to a blade that are due to changes in the handle or blade configuration. Similarly, in connection with machining tools such as a saw blade and milling tools, measurement of one or more of these parameters can be used to determine or predict the sharpness and cutting performance of the tool.
Sensor technology that can be integrated into semiconductor materials for sensing characteristics such as strain, pressure, temperature, density, the presence of nerves and movement are well known in the art. A strain sensor or gauge can be constructed using a resistor made of a material such as polysilicon. The resistance of a material such as polysilicon changes as it is stretched, and by measuring the change in resistance, one can calculate the strain. A pressure sensor can be constructed by placing a strain sensor on top of a diaphragm made of a material such as silicon nitride or polysilicon. When the diaphragm moves due to surrounding pressure changes, the strain gauge can be used to measure the local pressure. Examples of such pressure sensors are described in S. Sugiyama et al., xe2x80x9cMicro-diaphragm Pressure Sensor,xe2x80x9d IEEE Int. Electron Devices Meeting, 1986, pp. 184-7, and H. Tanigawa et al., xe2x80x9cMOS Integrated Silicon Pressure Sensor,xe2x80x9d IEEE Trans. Electron Devices, Vol. ED-32, No. 7, pp. 1191-5, July 1985, the disclosures of which are incorporated herein by reference.
One example of a temperature sensor can be constructed in a manner similar to a strain sensor using a resistor made of a material such as polysilicon. Using this type of a sensor, temperature can be measured as a function of the change in the resistance of the material. Similarly, as described in A. S. Sedra and K. C. Smith, xe2x80x9cMicroelectronic Circuits,xe2x80x9d 4th Ed., Oxford University Press, New York, p. 135, 1998, the disclosure of which is incorporated herein by reference, diodes have an easily measured temperature dependence and thus are also used in designing temperature sensors.
Piezoelectric ultrasonic sensors can be used to measure density. Such sensors vibrate at a high frequency and emit, in the direction of the object of interest, a high frequency signal. Density of the impinged object can then be measured based on the signal that is reflected back by that object. Examples of such sensors are described in White et al., U.S. Pat. No. 5,129,262, entitled xe2x80x9cPlate-mode Ultrasonic Sensor,xe2x80x9d White et al., U.S. Pat. No. 5,189,914, also entitled xe2x80x9cPlate-mode Ultrasonic Sensor,xe2x80x9d and S. W. Wenzel and R. M. White, xe2x80x9cA Multisensor Employing an Ultrasonic Lamb-wave Oscillator,xe2x80x9d IEEE Trans. Electron Devices, Vol. 35, No. 6, pp. 735-743, June 1988, the disclosures of which are incorporated herein by reference. It is well known to sense the presence of nerve tissue using an electrical contact, such as a gold electrode, which picks up and conducts electrical signals in proximity therewith.
Movement or motion can be detected using an accelerometer, which measures acceleration. The signal output of an accelerometer can be integrated to determine or predict the distance traveled by a reference object. An example of an accelerometer integrated into semiconductor materials is described in Sherman, S. J.; Tsang, W. K.; Core, T. A.; Quinn, D. E., xe2x80x9cA low cost monolithic accelerometer,xe2x80x9d 1992 Symposium on VLSI Circuits. Digest of Technical Papers, Seattle, Wash., USA, Jun. 4-6 1992, p. 34-5, the disclosure of which is incorporated herein by reference. This accelerometer operates by monitoring the deflection of a polysilicon structure, which can then be used to determine or predict acceleration, and is produced using the micromachining of layers of semiconductor materials using semiconductor processing techniques. Direction of movement or motion can be detected using a gyroscope. An example of a gyroscope that can be integrated into semiconductor materials described in Ayazi, F.; Najafi, K., xe2x80x9cDesign and fabrication of high-performance polysilicon vibrating ring gyroscope.xe2x80x9d Proc. IEEE MEMS 98, p. 621-6, 1998, the disclosure of which is incorporated herein by reference. This gyroscope operates by monitoring the movement of a vibrating ring of silicon to infer change in direction, and is produced using the micromachining of layers of semiconductor materials using semiconductor processing techniques.
Surgical tools constructed entirely of semiconductor materials, such as silicon, having the ability to sense, for example, temperature or strain, are known, examples of which are described in Carr et al., U.S. Pat. No. 5,980,518, entitled xe2x80x9cMicrocautery Surgical Tool,xe2x80x9d and Mehregany et al., U.S. Pat. No, 5,579,583, entitled xe2x80x9cMicrofabricated Blades.xe2x80x9d Using only semiconductor materials to construct the surgical tools is a natural approach since semiconductor materials such as silicon can be made with the requisite degree of sharpness and will also allow for direct fabrication of circuitry. However, semiconductor materials such as silicon tend to be brittle and hence not well suited for use as the primary structural component in a cutting device for surgical, industrial, and many consumer applications.
Described is a cutting instrument including a rigid blade having a recess formed therein and a semiconductor substrate affixed to the blade in the recess. The blade is preferably constructed of metal. The semiconductor substrate includes at least one sensor formed thereon. The sensor formed on the semiconductor substrate may comprise one or more of a strain sensor, a pressure sensor, a nerve sensor, a temperature sensor, a density sensor, an accelerometer, and a gyroscope. The sensor formed on the semiconductor substrate may also comprise an array of two or more of each sensor.
The recess in the blade is preferably formed so as to follow at least a portion of the edge of the blade. The semiconductor substrate may then be affixed to the blade in the recess adjacent the edge of the blade. The semiconductor substrate may also include circuitry formed thereon that is coupled to the sensors. The circuitry preferably includes one or more amplifiers and/or logic circuits for multiplexing the signals generated by the sensors.
The cutting instrument may also further include a handle wherein the blade is affixed to the handle and the semiconductor substrate is electrically coupled to the handle. The handle may then be coupled to a computer that is adapted to display information to a person using the cutting instrument based on signals generated by one or more of the sensors formed on the semiconductor substrate. The handle may include an electrical connector that is physically connected to a compatible connector associated with the computer, or may preferably include a wireless transmitter coupled the semiconductor substrate that is in communication with a wireless receiver associated with the computer. The handle or separate computer may also be adapted to store data based on the signals generated by one or more of the sensors.
Also described is a method of making a cutting instrument, including a semiconductor substrate having a defined shape and at least one sensor formed thereon. According to the method, at least one sensor is formed on a semiconductor wafer and a layer of photoresist is applied on a top side of the semiconductor wafer according to a pattern that matches the defined shape of the semiconductor substrate. The portion of the semiconductor wafer not covered by the photoresist is removed and thereafter the photoresist is removed from the semiconductor wafer, thereby leaving the semiconductor substrate having a defined shape and at least one sensor formed thereon utilizing techniques well known in the art. The semiconductor substrate having a defined shape and at least one sensor formed thereon is then affixed to a metal blade in a recess formed in said blade.
The semiconductor wafer may comprise a silicon-on-insulator wafer including a top layer of silicon, a middle layer of insulating material, and a bottom layer of silicon. The method would then include removing the bottom layer of silicon after applying the photoresist. An etching process may be used to remove the portion of the semiconductor wafer not covered by the photoresist and the bottom layer of silicon.
The semiconductor wafer may also comprise a silicon wafer. The method may then include grinding the wafer down to a desired thickness before affixing the semiconductor substrate to the blade.